Surveillance video depicting Trayvon Martin's killer hours after the teenager's death has cast doubt on his claims that he was injured in a vicious fight with the victim.

Seen in handcuffs and accompanied by police officers, self-appointed neighbourhood watchman George Zimmerman displays no obvious signs of having been attacked.

The CCTV footage has prompted further questions over Zimmerman's account of the incident. Earlier reports suggested that 17-year-old Martin had attacked the older man first, with the bloodied gunman pulling the trigger in self-defence.

According to police statement leaked to the Orlando Sentinel this week, Zimmerman was punched in the face before his head was pounded into the sidewalk by Martin during the incident.

The 28-year-old's account of the attack in Sanford, Florida, was said to have been confirmed by eyewitnesses.

Zimmerman's attorney, Craig Sonner, has said repeatedly that his client's nose was broken during the fight, which took place after Martin, an unarmed black teenager, noticed that the neighbourhood watchman had been trailing him from a local shop.

Reports had suggested that police responding to the incidents found Zimmerman bleeding from both his nose and the back of his head.

But CCTV footage, first released by ABC News, appears to cast doubt on the extent of the shooter's injuries.

In it, the 28-year-old's head and face are clearly visible. There appears to be no clear signs of any wounds. Likewise, there are no obvious indications of blood on the front of his T-shirt that could indicate evidence of a broken nose.

It was already known that the shooter was treated by paramedics at the scene, but the lack of any clear injuries has led some to suggest that they have been overstated.

Sanford police confirmed that the man in the video footage is Zimmerman.It shows him being escorted into a police station shortly after the incident on 26 February.

Responding to the latest development, Ben Crump, a lawyer for the Martin family, said: "This certainly doesn't look like a man who police said had his nose broken and his head repeatedly smashed into the sidewalk."

He added: "George Zimmerman has no apparent injuries in this video, which dramatically contradicts his version of the events of February 26."

Since that date, just over a month ago, anger has spread from the local community across the US, with protests and rallies demanding Zimmerman's arrest.

The neighbourhood watchman began following the unarmed teenager as he walked back to the home of his father's girlfriend.

The youth, who was serving out a school suspension at the time, was wearing a hooded top and was acting "suspiciously," his killer has said.

Zimmerman has said that he pulled the trigger after he was set upon by Martin in what one relative of the 28-year-old said was "a fight for his life."The shooter's father told Orlando TV station WOFL that Martin confronted his son, saying "something to the effect of, 'You're going to die now' or 'You're going to die tonight'."

He then pummelled the neighbourhood watchman so badly that armed man was forced to shoot, Robert Zimmerman added.

But claims of a racial element to the killing have added fuel to the growing disquiet over Zimmerman's subsequent release.

The level of anger directed against him has forced Zimmerman to go into hiding amid death threats directed toward both him and his family.

On Wednesday, film director Spike Lee was forced to apologise after he retweeted the home address of an elderly couple he believed to be connected to Zimmerman.

David and Elaine McClain, who are in their 70s and are unrelated to the case, have said that they were forced to leave their home out of safety concerns after the post was picked up by the moviemaker's 250,000 followers.

I Deeply Apologize To The McClain Family For Retweeting Their Address.It Was A Mistake.Please Leave The McClain's In Peace.Justice In Court

The original posting led to a torrent of racial abuse directed to Lee on the micro-blogging site. The director of Do the Right Thing and Malcolm X retweeted the racist messages, explaining to followers "this sickness must be exposed."

The incident highlights the way in which Martin's death has set off a debate over race relations in the US, with many commentators wondering if the teenager would have been killed had he been white.

Lawyers and family members of Zimmerman — the son of a white father and a Hispanic mother — have repeatedly denied claims that he acted out of any racial prejudice.

But the statements have done little to quiet the discontent surrounding his continued freedom.